Question : Multiple VPN connections from another NAT

I have some users out in a school district that need to VPN to our system. All of the internet access for all of these schools goes through one proxy for the whole city.

Currently I have a ISA server that they connect through via PPTP but the issue is that not more then one person can connect at a time as they are coming from the same public IP address and ISA does not seem to handle it.

I am looking for any solution for this situation. Can other VPN Appliances handle this type of connection?
We cannot put in a VPN device that all the users would connect through as they are at different physical locations in the city.

Thanks for the help

Answer : Multiple VPN connections from another NAT

ok lets get some more details, this is all very vague. What kind of system do they need access to? what are they connecting with dsl?t1?framerelay? wy not just have vpn clients for each pc?

solution:
Have a vpn concentrator in your main site and you are good to go. I have a wan with 13 locations remotely and about 10 users at each site, they come out with the same ip and all connect to my cisco concentrator with no problem.